Modulating and transmitting system



E. L. NELSON.

MODULATING AND TRANSMITTING SYSTEM.

WPUCATION mm MAR. 21. I918.

Patented Aug. 17, 1920.

W W V Ell till

UNITED STATES PATENT OFFICE.

EDWARD I. NELSON, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEG- TRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Application filed March 8,

T 0 all whom it may concern:

Be it known that I, EDWARD L. NELSON, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Modulating and Transmitting Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to oscillating and transmitting systems.

An object of the invention is to improve modulating and transmitting systems for signaling, and particularly for signaling by wireless methods. v

A particular object of the invention 1s to improve upon transmitting means of the kind stated in which a high frequency oscillation generator works directly into an antenna or transmitting conductor and wherein the currents generated by the high frequency generator are directly modulated by an associated low frequencygenerator.

A more general object is -to couple together oscillating audions or similar electric discharge devices in a new and useful manner.

An embodiment of the invention is illustrated diagrammatically in the accompanying drawing and consists in the combination of low frequency and high frequency vacuurn tube oscillators of the audion or threeelectrode type connected by such circuits that the high frequency oscillations are modulated in accordance with the low frequency oscillations. The frequency of the latter may be instantaneously changed by a key, thereby causing signals to be, transmitted.

The tube 0, which is of the audion or three-electrode type, functions as a high frequency oscillator and has an oscillation circuit consisting of aerial 1, coil 2, capacity 3 and conductor 1 to ground. The feedback potential is applied to the control electrode or grid by means of capacity 3 which is variable, through capacity 5 which is connected to the lower end of antenna coil '2. Leak resistance 6 connects the grid and filament in the usual manner and the plate or anode is variably connected to coil 2 through condenser 7.

Tube 0' functions as a modulating oscillatorand has an oscillating circuit including variable capacity 8, inductance 9, including a portion 10 and condenser 11. Stopping MODULATING- AND TRANSMITTING SYSTEM.

Specification of Letters Patent. Patented Aug. 1'7, 1320 to supply plate-filament current to both tubes through choke coil 17 which serves to keep constant the sum of the plate-filament currents. The inductance 18 acts as a high frequency choke and serves to prevent the high frequency oscillator from reacting upon the low frequency oscillator. Since coil 17 will always have considerable capacity reactance at high frequencies, coil 18 will also serve to annul the capacity effects of coil 17 in the circuit consisting of elements 1, 2, ,18, 17, 16, t to ground, through which clrcuit it is desirable that no high frequency current shall pass. Source of electromotive force 19 serves to heatthe filaments of the oscillators.

Operation: Since the impedance between the anode and the cathode of the tube 0 will vary substantially sinusoidally at the 2 frequency at which the adjustment of circuit 8, 9, 10 and 11 is, at any instant, causing it to oscillate, this will cause corresponding changes of voltage to be impressed across the. anode and the cathode of tube '0. Thus while the tube O is continually oscillating at a relatively high frequency compared to the frequency of the variations of impedance of the tube 0, the oscillations as set up by the tube 0 will continually vary in amplitude in accordance with the oscillations of O", on account of the variation in the anode cathode voltage impressed on the tube 0. From another aspect the coil 17 and source 16 may be regarded as a source of constant current which cannot undergo material changes during the period of onecycle of oscillator 0'. Then as O cyclically varies in impedance the space current therethrough varies correspondingly. When the tube 0 takes more space current the tube 0 must necessarily take less and viceversa. The amplitude of the oscillations of tube 0 will be an almost linear function of the instantaneous value of the space current therethrough. The variations of current through arrangement shown and described, which is merely illustrative. The various features of the invention, all of which are of more or less general application, are set forth in the appended claims.

What is claimed is:

1. In a transmitting system, an oscillation circuit including an antenna, a three-electrode vacuum tube associated with said circuit to generate oscillations therein, a second three-electrode vacuum tube associated with said first mentioned tube, an oscillation circuit for sai -second mentioned tube. a source of anode-cathode current for said tubes, a circuit through which the current is supplied, and means in said circuit for maintaining the sum of the currents through said tubes constant.

2. In a radio system, an oscillation circuit including an antenna, a means for generating oscillations therein including a three-electrode vacuum tube, a second oscillation circuit,'a second means for generating oscillations therein including a second three-electrode vacuum tube, a source of anode-cathode current for the tubes of said generating means, and a means tending to prevent fluctuation in the total current supplied by said source.

3. In combination, a pair of three-electrode vacuum tubes each producing oscillations in a different circuit, one electrode of each tube being a cathode, a negligible impedance connection between the cathodes and a conductive connection for the anodes having negligible impedance except for a filter element adapted to offer impedance to high frequencies.

' 4. In combination, a plurality of electrical discharge devices, individual frequency determining circuits for said devices, each said device including a cathode, an anode and a control element, a negligible impedance connection between the cathodes, and a conductive connection for the anodes of negligible impedance except for a filter means adapted to offer high impedance to high frequencies.

5.. In combination, a plurality of discharge devices, individual frequency determining circuits for said devices, each said device including a cathode and an anode, a negligible impedance connection between the cathodes, and a conductive connection between the anodes having. negligible im-- pedance except for an electrical impedance means adapted to offer impedance to high frequencies.

0'. In combination, a pair of three-electrode vacuum tubes, individual frequency determining circuits for said tubes, one electrode of each tube being a cathode, one electrode of each tube being an anode, a ne ligible impedance connection for the catho es, and a connection for the anodes which is of negligible impedance except for a coil adapted to offer a high impedance to oscillations of the approximate frequency at which the tube having the highest oscillation frequency is adapted to oscillate.

In combination, two oscillation circuits, a pair of three-electrode vacuum tubes each. primarily adapted to generate oscillations in one only of said circuits with which it is directly associated, a low impedance connection for one corresponding pair of said electrodes. and a direct connection including a high frequency obstructing element for another corresponding pair of said electrodes, and means tending to keep constant the sum of the anode currents supplied to said tubes.

t. In combination, a vacuum tube, means including feed-back'circuits therefor whereby the tube acts as a generator of oscillations, a second vacuum tube, other means therefor whereby the second tube acts as a generator of oscillations, means whereby the oscillations generated by the first of said tubes are modulated according to the oscillations generated by the second, and means for maintaining the sum of the anode currents through said tubes constant.

9. In combination, a three-electrode vacuum tube oscillating generating system, a second three-electrode vacuum tube oscillation generating system, two elements of each tube being an anode and a cathode, means whereby the oscillations of one system may be modulated according to the oscillations of the second, means for supplying anodecathode current, and means for keeping the sum of the anode-cathode currents of said systems constant.

10. In combination, an oscillation generating system including a discharge device, a second oscillation generating s stem including a discharge device, feedack connections for said systems, means for producing a space current in each system, means whereby the oscillations of one system may be modulated-according to the osailations of the second, and means for keepzng the sum of the space currents of said systems constant.

11. In combination, a plurality of oscillation generating systems, each said system including an electrical discharge device having an impedance controlling element, an anode and a cathode, means for producing an anode-cathode current in each system, and means for keeping the sum of the anodecathode currents of said systems constant.

12. In combination, a plurality of connectedoscillation generating systems, each having a discharge device including an anode, a cathode and a control element, and means for keeping the sum of the anodecathode currents of said systems constant.

13. In combination, a plurality of connected oscillation generating systems, each having a discharge device including an anode and a cathode, a feed-back for each discharge device and means for keepin the sum of the anode-cathode currents 0 said systems constant.

In witness whereof I hereunto subscribe my name this first day of November, A. D.

EDWARD L. NELSON. 

